Flueless domestic gas water heater - has fusible link safety cut out to detect blockage of flue ways

摘要

The heater has a casing (5) containing a finned tube heat exchanger (1) above a combustion space (4) with a draught limiting flue gas outlet (2) at the top. A gas burner (6) is positioned below the combustion space and a flame failure circuit containing a thermocouple element (15) heated by the pilot flame (16). This circuit also contains a fusible link (3) placed near but not touching the casing opposite a small orifice (17) near the bottom of the casing. In normal operation rising flue gases draw air in through this orifice. If the passages through the heat exchanger (1) become blocked hot flue gases are forced to escape through the orifice and heat the fusible link until it melts and breaks the circuit which holds the main gas solenoid valve open.